The invention relates to stress testing device mounting apparatus and in particular to apparatus for use in the in situ stress testing of materials. More particularly, the stress testing apparatus provides variable tensile and compressive loads for the in situ stress testing of materials.
GB-A-2263341 discloses a device for performing fatigue tests on materials. The device is capable, in different embodiments, of subjecting materials to tensile or compressive stresses. Previously, fatigue tests required large, bulky equipment which necessitated tests being carried out in the laboratory or in static outdoor test environments. Laboratory testing is limited in that there are certain xe2x80x9creal lifexe2x80x9d conditions which are very difficult artificially to replicate. The device disclosed in GB-A-2263341 has because of its size and simplicity enabled fatigue tests to be carried out away from the laboratory in real life environments. For instance, structural bonding systems for vehicle applications have been tested by mounting the devices on working vehicles so as to expose the system to real life variations in temperature, humidity and mechanical stress. However, when a number of materials are to be tested, in the same environment, the number of devices involved may result in the mounting of the devices and connections to them becoming complex and problematic.
The invention provides apparatus for mounting a plurality of stress testing devices comprising a cylinder block including a plurality of cylinders, a plurality of pistons each housed in one of the cylinders, means for conveying pressurised fluid from a source to each piston and means for attaching each device to the cylinder block at a position which enables the device to interact with a respective one of the pistons.
The apparatus according to the invention enables a plurality of testing devices to be conveniently located in the same position in an in-situ testing environment without the need for complex or extensive associated connections: Each device may operate from a single source of pressurised hydraulic fluid. The apparatus may be adapted to mount any number of testing devices. The apparatus may be fully or partially submerged in a liquid environment if so desired.
Preferably, the devices are releasably attached to the cylinder block and may be released without significantly affecting the pressure of the fluid and therefore the operation of the remaining devices. Each piston may be arranged so as to be retained in its respective cylinder whether or not a device is mounted to interact with that piston and adequate sealing means provided to prevent hydraulic fluid leaking past the piston.
Further preferably, the pressure of the fluid is varied in a random manner. The variations may be produced by monitoring a random event and translating that random event into a pressure value. Alternatively, the pressure of the fluid could be varied in a regular fashion, for instance, with a pump operated on a sinusoidal cycle.
The devices may subject the specimens under test to tensile stresses, compressive stresses or a combination of the two. Devices of the type shown in GB-A-2263341 are particularly suited to use with the apparatus according to the invention.